Browsing by Author "Bertarini, A."
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Item Completing the K-band Celestial Reference Frame in the Southern Hemisphere(IVS Publications, 2014) de Witt, A.; Bertarini, A.; Horiuchi, S.; Jacobs, C.S.; Jung, T.; Lovell, J.E.J.; McCallum, J.N.; Quick, J.F.H.; Sohn, B.W.; Phillips, C.; Ojha, R.K-band (22 GHz) radio observations have the potential to form the basis for the most accurate Celestial Reference Frame(CRF) ever constructed. Relative to the standard S/X (2.3/8.4 GHz) observing bands, K-band is expected to exhibit a reduction in extended source morphology and core-shift. This reduction in astrophysical systematics should allow for a more stable CRF at K-band and should also be advantageous in tying the VLBI radio frame to the Gaia optical frame. K-band CRF observations currently exist only from the all-northern Very Long Baseline Array (VLBA) and therefore must be complimented by observations from southern arrays in order to realize this potential. A collaboration was formed with the goal of completing sky coverage at K-band with specific emphasis on the Southern Hemisphere where K-band CRF coverage is weak. Southern hemisphere observations to densify the CRF at K-band are under way and preliminary astrometric observations were carried out on 23 August 2013 between telescopes in Australia (Hobart 26m), Korea (Tamna 21m), and South Africa (HartRAO 26m). More extensive astrometric observations were carried out on 21/22 December 2013 that also included the Tidbinbilla 70-m DSN antenna in Australia. A proposal for imaging source structure at K-band has been submitted to the Australian Telescope-Long Baseline Array (AT-LBA). We discuss some of our results as well as the implications for K-band CRF work.Item Extending the K-band Celestial Frame Emphasizing Southern HemisphereWitt, A. De; Bertarini, A.; Horiuchi, S.; Jacobs, C.S.; Jung, T.; Lovell, J.E.J.; McCallum, J.N.; Quick, J.F.H.; Sohn, B.W.; Ojha, R.K-band radio observations have the potential to form the basis for the most accurate celestial reference frame (CRF) ever constructed. We present a new collaboration to observe southern hemisphere extra-galactic radio sources at 22 GHz (K-band). The aim of this project is to densify the ICRF at that frequency and to provide calibrators for astronomy. Relative to the standard S/X observing bands, at K-band sources are expected to exhibit more compact source morphology and reduced core shift. This reduction of astrophysical systematics should be advantageous in tying the VLBI radio frame to the Gaia optical frame. Initial fringe demonstrations were carried out on 23 August 2013 between telescopes in Australia, Korea and South Africa. The Korea to South Africa baselines will extend Kband CRF coverage down to about −45◦ declination. Observations between Australia and South Africa will extend coverage to the south polar cap and thus gain full sky coverage for the K-band CRF. The second phase of our plan includes more extensive astrometric observations to complete sky coverage at K-band as well as observations using a larger network of telescopes in an effort to image source structure.